Notebook computers are portable computing devices that have become very popular in recent years. Two components that contribute to their portability are the battery and the voltage regulator.
The battery supplies electrical power to the device, typically at a voltage level of 9-13 volts. However, this voltage level is typically higher than the voltage needed by many of the components in these devices. For example, a microprocessor—the brains of the computer—typically operates on approximately one to two volts. Converting the battery voltage to the right level for any given component is the job of the voltage regulator.
In addition to converting the voltage, the voltage regulator has the job of reducing fluctuations in its output voltage as demand for power fluctuates in response to changes in component workload. For example, when a microprocessor shifts from idle to active, it pulls the regulator output voltage downward from its desired level, and conversely, when the microprocessor shifts from active to idle, it pushes the regulator output voltage upward. In either case, a properly functioning voltage regulator quickly responds to the changing load conditions by increasing or decreasing its output voltage to counteract effects of loading. A consequence of the changing load and voltage levels is that the regulator output voltage generally ripples or oscillates back and forth about its desired voltage.
To reduce the magnitude of these ripples and their undesirable effects on processor operations, many computing devices employ a multi-phase voltage regulator. These multi-phase voltage regulators often include two or more separate inductors that are connected so that ripples at the output of one phase are opposite in direction or polarity to ripples on the other phase. The outputs of the two phases are added together, with the opposing ripples partially canceling each other and reducing the magnitude of ripples that reach the microprocessor.
At least one problem recognized by the inventors is that conventional multi-phase voltage regulators often use separate inductors which not only occupy significant space on the motherboard—that is, the printed circuit board that carries many components of the computer system—but also necessitate the use of other large components, such as several 300 microfarad capacitors. Thus, the use of separate inductors ultimately limits the ability of manufacturers to further reduce the size of the motherboard or to add other components to the same size motherboard.
Accordingly, the inventors have recognized a need for alternative circuitry for voltage regulators.